HONOLULU — U.S. Coast Guard Pollution investigators determined this morning there is no threat of marine pollution after a U.S. Navy ship was freed from a grounding site off Honolulu International Airport’s reef runway.

The USS Port Royal ran aground a half mile off the runway Thursday and was pulled free early this morning by the Navy. A Coast Guard air crew aboard an HH-65 Dolphin helicopter was airborne for an investigation at sunrise.

Coast Guard pollution investigators aboard the HH-65 reported a sheen of approximately one mile by 100 yards wide. Pollution investigators on scene on Coast Guard vessels report the sheen is marine diesel, a very thin fuel which burns off quickly in sunlight.

The Coast Guard estimates the amount of fuel comprising the sheen is approximately seven to eight gallons. It’s not clear yet if the fuel is from the Port Royal or from one of the nine other vessels used in the response.

There is no threat to the coastline or marine life from the sheen and a crew aboard the oil spill recovery vessel Clean Islands will remain on scene until the sheen burns away.

“We are confident the small sheen will burn away this morning,” said Cdr. Kathleen Moore, the U.S. Coast Guard Alternate Captain of the Port and a senior officer responsible for oil spill response in the main Hawaiian Islands.